/*
 * Copyright (C) 2009 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.android.apis.graphics;

import java.io.IOException;
import java.io.InputStream;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;

import javax.microedition.khronos.egl.EGLConfig;
import javax.microedition.khronos.opengles.GL10;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.opengl.GLES20;
import android.opengl.GLSurfaceView;
import android.opengl.GLUtils;
import android.opengl.Matrix;
import android.os.SystemClock;
import android.util.Log;

import com.example.android.apis.R;

class GLES20TriangleRenderer implements GLSurfaceView.Renderer {

	public GLES20TriangleRenderer(Context context) {
		mContext = context;
		mTriangleVertices = ByteBuffer
				.allocateDirect(mTriangleVerticesData.length * FLOAT_SIZE_BYTES)
				.order(ByteOrder.nativeOrder()).asFloatBuffer();
		mTriangleVertices.put(mTriangleVerticesData).position(0);
	}

	public void onDrawFrame(GL10 glUnused) {
		// Ignore the passed-in GL10 interface, and use the GLES20
		// class's static methods instead.
		GLES20.glClearColor(0.0f, 0.0f, 1.0f, 1.0f);
		GLES20.glClear(GLES20.GL_DEPTH_BUFFER_BIT | GLES20.GL_COLOR_BUFFER_BIT);
		GLES20.glUseProgram(mProgram);
		checkGlError("glUseProgram");

		GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
		GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, mTextureID);

		mTriangleVertices.position(TRIANGLE_VERTICES_DATA_POS_OFFSET);
		GLES20.glVertexAttribPointer(maPositionHandle, 3, GLES20.GL_FLOAT,
				false, TRIANGLE_VERTICES_DATA_STRIDE_BYTES, mTriangleVertices);
		checkGlError("glVertexAttribPointer maPosition");
		mTriangleVertices.position(TRIANGLE_VERTICES_DATA_UV_OFFSET);
		GLES20.glEnableVertexAttribArray(maPositionHandle);
		checkGlError("glEnableVertexAttribArray maPositionHandle");
		GLES20.glVertexAttribPointer(maTextureHandle, 2, GLES20.GL_FLOAT,
				false, TRIANGLE_VERTICES_DATA_STRIDE_BYTES, mTriangleVertices);
		checkGlError("glVertexAttribPointer maTextureHandle");
		GLES20.glEnableVertexAttribArray(maTextureHandle);
		checkGlError("glEnableVertexAttribArray maTextureHandle");

		long time = SystemClock.uptimeMillis() % 4000L;
		float angle = 0.090f * ((int) time);
		Matrix.setRotateM(mMMatrix, 0, angle, 0, 0, 1.0f);
		Matrix.multiplyMM(mMVPMatrix, 0, mVMatrix, 0, mMMatrix, 0);
		Matrix.multiplyMM(mMVPMatrix, 0, mProjMatrix, 0, mMVPMatrix, 0);

		GLES20.glUniformMatrix4fv(muMVPMatrixHandle, 1, false, mMVPMatrix, 0);
		GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, 3);
		checkGlError("glDrawArrays");
	}

	public void onSurfaceChanged(GL10 glUnused, int width, int height) {
		// Ignore the passed-in GL10 interface, and use the GLES20
		// class's static methods instead.
		GLES20.glViewport(0, 0, width, height);
		float ratio = (float) width / height;
		Matrix.frustumM(mProjMatrix, 0, -ratio, ratio, -1, 1, 3, 7);
	}

	public void onSurfaceCreated(GL10 glUnused, EGLConfig config) {
		// Ignore the passed-in GL10 interface, and use the GLES20
		// class's static methods instead.
		mProgram = createProgram(mVertexShader, mFragmentShader);
		if (mProgram == 0) {
			return;
		}
		maPositionHandle = GLES20.glGetAttribLocation(mProgram, "aPosition");
		checkGlError("glGetAttribLocation aPosition");
		if (maPositionHandle == -1) {
			throw new RuntimeException(
					"Could not get attrib location for aPosition");
		}
		maTextureHandle = GLES20.glGetAttribLocation(mProgram, "aTextureCoord");
		checkGlError("glGetAttribLocation aTextureCoord");
		if (maTextureHandle == -1) {
			throw new RuntimeException(
					"Could not get attrib location for aTextureCoord");
		}

		muMVPMatrixHandle = GLES20.glGetUniformLocation(mProgram, "uMVPMatrix");
		checkGlError("glGetUniformLocation uMVPMatrix");
		if (muMVPMatrixHandle == -1) {
			throw new RuntimeException(
					"Could not get attrib location for uMVPMatrix");
		}

		/*
		 * Create our texture. This has to be done each time the surface is
		 * created.
		 */

		int[] textures = new int[1];
		GLES20.glGenTextures(1, textures, 0);

		mTextureID = textures[0];
		GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, mTextureID);

		GLES20.glTexParameterf(GLES20.GL_TEXTURE_2D,
				GLES20.GL_TEXTURE_MIN_FILTER, GLES20.GL_NEAREST);
		GLES20.glTexParameterf(GLES20.GL_TEXTURE_2D,
				GLES20.GL_TEXTURE_MAG_FILTER, GLES20.GL_LINEAR);

		GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_WRAP_S,
				GLES20.GL_REPEAT);
		GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_WRAP_T,
				GLES20.GL_REPEAT);

		InputStream is = mContext.getResources().openRawResource(R.raw.robot);
		Bitmap bitmap;
		try {
			bitmap = BitmapFactory.decodeStream(is);
		} finally {
			try {
				is.close();
			} catch (IOException e) {
				// Ignore.
			}
		}

		GLUtils.texImage2D(GLES20.GL_TEXTURE_2D, 0, bitmap, 0);
		bitmap.recycle();

		Matrix.setLookAtM(mVMatrix, 0, 0, 0, -5, 0f, 0f, 0f, 0f, 1.0f, 0.0f);
	}

	private int loadShader(int shaderType, String source) {
		int shader = GLES20.glCreateShader(shaderType);
		if (shader != 0) {
			GLES20.glShaderSource(shader, source);
			GLES20.glCompileShader(shader);
			int[] compiled = new int[1];
			GLES20.glGetShaderiv(shader, GLES20.GL_COMPILE_STATUS, compiled, 0);
			if (compiled[0] == 0) {
				Log.e(TAG, "Could not compile shader " + shaderType + ":");
				Log.e(TAG, GLES20.glGetShaderInfoLog(shader));
				GLES20.glDeleteShader(shader);
				shader = 0;
			}
		}
		return shader;
	}

	private int createProgram(String vertexSource, String fragmentSource) {
		int vertexShader = loadShader(GLES20.GL_VERTEX_SHADER, vertexSource);
		if (vertexShader == 0) {
			return 0;
		}

		int pixelShader = loadShader(GLES20.GL_FRAGMENT_SHADER, fragmentSource);
		if (pixelShader == 0) {
			return 0;
		}

		int program = GLES20.glCreateProgram();
		if (program != 0) {
			GLES20.glAttachShader(program, vertexShader);
			checkGlError("glAttachShader");
			GLES20.glAttachShader(program, pixelShader);
			checkGlError("glAttachShader");
			GLES20.glLinkProgram(program);
			int[] linkStatus = new int[1];
			GLES20.glGetProgramiv(program, GLES20.GL_LINK_STATUS, linkStatus, 0);
			if (linkStatus[0] != GLES20.GL_TRUE) {
				Log.e(TAG, "Could not link program: ");
				Log.e(TAG, GLES20.glGetProgramInfoLog(program));
				GLES20.glDeleteProgram(program);
				program = 0;
			}
		}
		return program;
	}

	private void checkGlError(String op) {
		int error;
		while ((error = GLES20.glGetError()) != GLES20.GL_NO_ERROR) {
			Log.e(TAG, op + ": glError " + error);
			throw new RuntimeException(op + ": glError " + error);
		}
	}

	private static final int FLOAT_SIZE_BYTES = 4;
	private static final int TRIANGLE_VERTICES_DATA_STRIDE_BYTES = 5 * FLOAT_SIZE_BYTES;
	private static final int TRIANGLE_VERTICES_DATA_POS_OFFSET = 0;
	private static final int TRIANGLE_VERTICES_DATA_UV_OFFSET = 3;
	private final float[] mTriangleVerticesData = {
			// X, Y, Z, U, V
			-1.0f, -0.5f, 0, -0.5f, 0.0f, 1.0f, -0.5f, 0, 1.5f, -0.0f, 0.0f,
			1.11803399f, 0, 0.5f, 1.61803399f };

	private FloatBuffer mTriangleVertices;

	private final String mVertexShader = "uniform mat4 uMVPMatrix;\n"
			+ "attribute vec4 aPosition;\n" + "attribute vec2 aTextureCoord;\n"
			+ "varying vec2 vTextureCoord;\n" + "void main() {\n"
			+ "  gl_Position = uMVPMatrix * aPosition;\n"
			+ "  vTextureCoord = aTextureCoord;\n" + "}\n";

	private final String mFragmentShader = "precision mediump float;\n"
			+ "varying vec2 vTextureCoord;\n" + "uniform sampler2D sTexture;\n"
			+ "void main() {\n"
			+ "  gl_FragColor = texture2D(sTexture, vTextureCoord);\n" + "}\n";

	private float[] mMVPMatrix = new float[16];
	private float[] mProjMatrix = new float[16];
	private float[] mMMatrix = new float[16];
	private float[] mVMatrix = new float[16];

	private int mProgram;
	private int mTextureID;
	private int muMVPMatrixHandle;
	private int maPositionHandle;
	private int maTextureHandle;

	private Context mContext;
	private static String TAG = "GLES20TriangleRenderer";
}
